Why are these great?
Fit, balance, cohesiveness.
No one's perfect; fewer "fits" are perfect. For example, I would have chosen a different square for @justinkapur, but it's still very nice; the colors still complement each other.
@Newcomer has balance in contrast. Note how the shirt and trousers are light, whereas the jacket and tie are dark. This is a tried and true combination that every man should have at the ready.
@justinkapur displays good tie/shirt pattern...